Body Systems - Osmoregulation and Excretion

Non-AP Bio 20 content

Osmolarity

Total concentration of solute particles. Determines movement of water. Milliosmoles per litre (mosm/L)

Hyperosmotic

Solution with higher solute concentration

Hypoosmotic

Solution with lower solute concentration

Osmoregulation

Freshwater

• Hypoosmotic, water flows in to cells, salt loss

Saltwater

• Hyperosmotic, water lost from cells

Land

• Dry environment, need to conserve water/salt

Intracellular Waste

Waste produced by chemical digestion. Deamination produces ammonia (highly toxic)

Deamination

Excess proteins converted to carbs through removal of amine group. Occurs in liver and produces ammonia (highly toxic)

Urea

Molecule formed by liver. Made of CO2 and 2 NH3. Less toxic than ammonia. Excreted through kidneys

Uric Acid

Least toxic form of ammonia, produced during break down of nucleic acids. Excreted through kidneys. Found in eggs

Freshwater Animals + Ammonia

Use surplus water to dilute ammonia and excrete it. Diffuses through gills/moist membranes. To overcome loss of salts, reabsorbed in kidneys or actively transported in

Land Animals + Ammonia

Need to conserve water, processes ammonia to be less toxic (urea). Filtered out through kidneys and urine. Urine highly concentrated

Egg-laying land animals + Ammonia

No place to get rid of ammonia in eggs, becomes uric acid

Uric Acid

Polymerized urea that precipitates out of solution

Key Functions of Mammalian System

1. Filtration

   • Water/solutes filtered out of blood

2. Re-absorption

   • Selectively reabsorb water and solutes when needed (diffusion)

3. Secretion

   • Pumping out unwanted solutes to urine

4. Excretion

   • Expel concentrated urine (Nitrogen waste, extra water/solutes, toxins) from body

Parts of Excretory System

1. Kidneys

2. Renal Arteries/Veins

3. Adrenal gland

4. Ureter

5. Bladder

6. Urethra

7. Aorta

8. Inferior Vena Cava

9. Urinary sphincter

Parts of a kidney

1. Renal Artery

2. Renal Medulla

3. Renal Cortex

4. Renal Pelvis

5. Renal Vein

6. Ureter

7. Nephrons

Kidneys

Regulate blood electrolyte concentration and eliminate waste from blood. Filter blood to form filtrate (both toxins and useful products).

1. Blood enters through renal artery, carried away by renal vein

2. Outer layer = cortex, Inner layer = medulla, Renal Pelvis = hollow chamber to join to ureter

Nephrons

Functional units of the kidneys, filter blood and produce urine

1. Blood enters through afferent arteriole

2. Filtrate is separated from blood

3. Blood goes through glomerulus. Blood leaves through efferent arteriole and waste (filtrate) goes to Bowman’s capsule

4. Passes through proximal tubule, loop of Henle, distal tubule and collecting duct

Parts of nephrons

1. Glomerulus

2. Bowman’s capsule

3. Proximal tubule

4. Loop of Henle (sets up concentration gradient)

5. Distal Tubule

6. Collecting Duct

Urine Formation

1. Filtration

   • Fluid goes from blood to Bowman’s capsule

2. Reabsorption

   • Solutes from nephron go back to blood

3. Secretion

   • Transport of materials from blood to nephrons

Nephron Filtration

Glomerulus

• water, glucose, salts/ions, urea filtered out

• Blood proteins and cells too large to be filtered out

High blood pressure in kidneys

Force water and solutes out of blood vessels - hydrostatic pressure. High blood pressure in system can cause kidney damage (Big issue)

Reabsorption

Aldosterone - hormone to increase reabsorption of Na+ and water by kidneys. Helps maintain body fluid levels. Occurs until threshold level where excess is secreted with urine. Creates osmotic gradient, draws water into blood from nephron. Proteins in blood also create osmotic force that takes water from interstitial fluid into blood. Primarily occurs in loop of Henle

Loop of Henle

Descending limb highly permeable to water, many aquaporins

Ascending limb highly permeable to salts/solute, few aquaporins

Creates/maintains concentration gradient

Distal tubule

Reabsorbs salts, water, bicarbonate. Leads to collecting duct

Collecting Duct

Reabsorbs water. Permeability to water and urea changes with ADH and aldosterone. Excretes urine to bladder

Secretion

Movement of fluids from blood to nephrons by active transport

Peritubular Capillary Bed

Capillaries that wrap around nephrons

pH Balance

CO2 actively transported by peritubular capillaries (kidney capillaries) into cells that line nephron to create bicarbonate and hydrogen ions. Acts as buffer solution. Excess H+ secreted after combining with phosphate ions or ammonia

ADH (Antidiuretic hormone)

Released by pituitary gland to regulate osmotic pressure of body fluids. Increases water reabsorption in kidneys. Makes up upper part of distal tubing/collecting duct, produces more concentrated urine. Osmoreceptors in hypothalamus detect osmotic changes and release ADH. Creates sensation of thirst

Diuresis

Increased urine production

Aldosterone

Hormone produced in adrenal cortex that increases Na+ reabsorption. Triggered by low blood pressure/volume. Part of RAAS

RAAS

Renin → Angiotensin → Aldosterone system. Causes blood vessel constriction, increases water and NaCl reabsorption

Uses of the 2 Systems

ADH

• Blood osmolarity

  • Increased water absorption

RAAS

• Blood volume

  • Increased salt and water absorption

  • Aldosterone

Diabetes Mellitus

Inadequate secretion of insulin, higher blood sugar levels

Type I - Decreased insulin production

Type II - Decreased insulin recognition

Diabetes Insipidus

Destruction of ADH-producing cells or nerves that bring ADH to pituitary gland. Causes increased thirst and excessive urinating

Nephritis

Inflammation of the nephrons. Can destroy capillaries of glomerulus - allows large molecules to pass through (proteins in urine) or can draw more water into nephron and increase urine output

Kidney Stones

Blockages caused by minerals and crystalized salts from blood

Dialysis

Sending blood out for external cleaning because the kidneys can’t do their job

Urinalysis

Method to detect kidney disorders

Kidney transplant

Treatment that fully replaces a broken kidney